Field of the Invention
The present invention relates to a magnetic recording medium and to a method of manufacturing the same. More particularly, the present invention relates to a magnetic recording medium capable of possessing both good electromagnetic characteristics and durability, and to a method of manufacturing the same.
Discussion of the Background
Conventionally, primarily ferromagnetic metal powder has come to be employed in the magnetic layers of magnetic recording media for high density recording. Ferromagnetic metal magnetic powder includes acicular particles comprised primarily of iron, and has come to be employed in magnetic recording media for various uses in which a reduction in particle size and high coercive force are sought in high density recording.
With an increase in the quantity of information being recorded has come a constant demand for high-density recording in magnetic recording media. However, in trying to achieve higher density recording, limits to the improvement of ferromagnetic metal magnetic particles have begun to appear.
By contrast, hexagonal ferrite magnetic powder has a coercive force that is high enough for use in permanently magnetic materials, and a magnetic anisotropy, which is the basis of coercive force and is derived from a crystalline structure, that makes it possible to maintain high coercive force even when the size of magnetic particles is reduced. Further, magnetic recording media with magnetic layers in which hexagonal ferrite magnetic powder is employed afford good high-density characteristics due to their vertical component. Such hexagonal ferrite magnetic powder is ferromagnetic material that is suited to higher densities.
In recent years, as recording densities have continued to rise, recording densities of 1 Gbpsi and above, even 10 Gbpsi and above, have been targeted as surface recording densities. To that end, attempts have been made to reduce noise by further reducing the size of microparticles of ferromagnetic hexagonal ferrite powder, thereby enhancing the electromagnetic characteristics (signal/noise ratio (SNR)). In this regard, Japanese Unexamined Patent Publication (KOKAI) No. 2012-204726 or English language family member US2012/251844A1, which are expressly incorporated herein by reference in their entirety, proposes adjusting the composition of hexagonal ferrite to obtain ferromagnetic hexagonal ferrite powder that satisfies the three characteristics known as the magnetic recording trilemma: higher density recording (smaller microparticles in magnetic powder), thermal stability, and ease of writing.